Foot protection against Crushing Safety sign - This is a mandatory sign that stipulates that steel-tipped shoes must be worn to prevent crushing of your foot. This sign is often used to inform workers or visitors on specific sites what P.P.E. they require upon entering a Construction site, Mine, or even a workshop. This sign is used in conjunction with various other safety signs depending on what your requirements are, i.e - (ZM 20) Overall safety sign.